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Some journal articles just kind of jump out and make you wonder. Consider “Testicular volume is inversely correlated with nurturing-related brain activity in human fathers.” Rough translation: guys with smaller giggle berries are better at taking care of, if not necessarily making, babies. How do they get this stuff? Well, there’s a story here.

Researchers at Emory University posted flyers around campus, at parks and daycares, and on Facebook recruiting biological fathers of one to two-year-old babies who were willing come in with their kiddo and the child’s mother. The dads had to have no history of head trauma or “ferrous metal in any part of the body,” for reasons that will become clear later.

The babies were photographed making happy, sad and neutral facial expressions. What if they didn’t do that during the photo sessions? The investigators used “singing, dancing or tickling” to elicit happiness. To get the sad face, it was “mother leaving the room or taking a favourite toy or cellphone from the child.”

Armed with these photos, the researchers put the fathers into a Magnetic Resonance Imaging (MRI) machine to analyze their brains, also stopping off to take an MRI image of their testicles to calculate their volume. This explains the exclusion of people with metal plates or still-embedded bullets in their bodies. Those things don’t do well in MRI machines.

If this doesn’t show that medical research can be highly entertaining, consider the observation that “one participant’s testes volume measurement was excluded because his value was 2.8 standard deviations above the mean ... and more than 13,000 cubic millimetres larger than any recorded value found in the literature.” Apparently, you meet the oddest people when you put up flyers around campus.

The fathers were shown photographs of their own toddler, as well as an unknown child and adults, all making happy, sad and neutral faces. It turned out that some men showed significantly increased activity in the ventral tegmental area (VTA) of the brain when they viewed their own babies. This region is known to be a kind of pleasure centre. In fact, it’s where many commonly abused drugs have their effect.

Men with high VTA activity in response to their babies also tended to have smaller testicles and lower testosterone levels, and to score higher on a parenting questionnaire filled out by the child’s mother. The research doesn’t really address the question of causality: do men with smaller gonads make more attentive dads, or does doing the daddy job somehow cause shrinkage? Another huge issue is whether the questionnaire which asks things like who gives the child provides a true picture of the father’s responsibility. Perhaps he’s working two jobs and can’t devote quality time to his offspring.

While they dodge cause and effect, the authors do speculate about a trade-off between mating and parenting behaviour. They invoke Life History Theory, which says that “given that organisms have finite amounts of energy to expend on reproduction, evolution optimizes the allocation of resources toward either mating or parenting so as to maximize fitness.”

So, they explain, “low levels of testosterone are associated with reduced libido and high levels predict mating success.” They also note that in married couples, “testosterone levels are negatively correlated with relationship quality and high levels predict divorce.”

This research provides an excellent balance to the barrage of commercials urging men to take testosterone supplements to boost their energy and libido. While these may be appropriate in some cases, it’s also good to realize that there are some benefits to a lower testosterone level.

It’s been suggested that oxytocin, the “love hormone” that’s released during pregnancy and orgasm may be useful for dads who have trouble bonding with their babies. The scientists who did the Emory University study are now trying to see if a nasal spray of oxytocin can improve paternal motivation.

Oxytocin may also keep guys from fooling around. Researchers in Germany discovered that a whiff of this stuff caused men who were in a monogamous relationship to keep a greater distance between themselves and an attractive “temptress researcher.” In a study in the Journal of Neuroscience, Dirk Scheele and colleagues suggest that oxytocin “may help to promote fidelity within monogamous human relationships” by keeping men from signalling romantic interest through close-approach behaviour. The problem is the effect doesn’t last very long, so you’d have to be coming directly from an orgasmic or nasal spray encounter for it to make much of a difference.

If you see a guy giving himself a quick spray of oxytocin before heading into an office full of attractive ladies, he might be trying to avoid temptation. If, on the other hand, he’s slapping on a testosterone patch, his intentions might be somewhat different.

Dr. Tom Keenan is an award-winning journalist, public speaker and professor in the faculty of environmental design at the University of Calgary.

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